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. 2013 Oct 1;14(10):19846–19866. doi: 10.3390/ijms141019846

Figure 6.

Figure 6

Pathways for the formation of polyol and ROS. Glucose in the presence of AR and NADPH is reduced, forming sorbitol and NADP+; then sorbitol is oxidized in the presence of SDH and NAD+, forming fructose and NADH. During the reduction of glucose to sorbitol, together, oxidized glutathione is reduced to two molecules of glutathione by glutathione reductase in the presence of NADPH. In conditions of larger amounts of glucose to sorbitol reduction, lower levels of NADPH are available for the reduction reaction of oxidized glutathione to glutatione, with an increase of ROS. In higher oxidation of sorbitol to fructose, there will be a higher availability of NADH that in the presence of NADH oxidase and oxygen, increases the release of superoxide anion radical, with consequent increase of ROS release. AR, aldose reductase; NADPH, reduced nicotinamide adenine dinucleotide phosphate; NADP+, oxidized nicotinamide adenine dinucleotide phosphate; GSSG, oxidized glutathione; GSR, glutathione reductase; GSH, reduced glutathione; ROS, reactive oxygen species; NAD+, oxidized nicotinamide adenine dinucleotide; SDH, sorbitol dehydrogenase; NADH, reduced nicotinamide adenine dinucleotide; NADH oxidase, nicotinamide adenine dinucleotide oxidase.